1. Field of the Invention
The present invention relates to vehicle lamps and vehicle lamp systems used in automobiles or the like.
2. Description of the Related Art
Typically, a vehicle lamp can switch between a low beam and a high beam. The low beam illuminates a close range at a predetermined illuminance. Light-distribution patterns of the low beam are regulated so as not to cause glare to oncoming vehicle or leading vehicle, and the low beam is used mainly when the vehicle travels in a city area. Meanwhile, the high beam illuminates a distant, broad range in front at a relatively high illuminance and is used mainly when the vehicle travels at high speed on a road with little oncoming vehicle or little leading vehicle. Thus, the high beam provides better visibility for the driver than the low beam does but disadvantageously causes glare to a driver of a leading vehicle or of an oncoming vehicle or to a pedestrian.
In recent years, a technique for dynamically and adaptively controlling a high-beam light-distribution pattern based on conditions surrounding a vehicle has been proposed (see, for example, JP2008-137516). According to this technique, the presence of a leading vehicle, an oncoming vehicle, or a pedestrian is detected, and light in a region corresponding to the detected vehicle or pedestrian is attenuated so as to reduce glare to the vehicle or pedestrian.
Typically, in a conventional vehicle lamp system, regardless of whether the luminance is lowered to a level at which the lamp remains on at reduced luminance or to a level at which the lamp is off in order to reduce glare to a vehicle or a pedestrian, the luminance is gradually lowered to target luminance indiscriminately in the same period of time. This may be preferable in terms of simplifying control but leaves room for improvement in terms of the comfort for the driver.